Since the early development by Snellen of his acuity test in 1862, optotypes and combinations thereof, including both letters and numbers, have been used for visual acuity testing. Such testing is necessary for determination of lens correction, detection of impairment of vision, assessment of the effects of medical or surgery therapy, screening testing, qualifying testing, determining the degree of observation of spatial detail and the like. In each instance, the various systems and optotypes which attempt to improve the standardization of acuity testing by the use of various letters or designs are limited in uniformity by having variability of optotype recognition difficulty.
When utilizing the visual acuity charts, which have been developed to date, it is recognized that accuracy depends upon whether the chart letters are equally legible or whether some blur interpretation may be characteristic of the configuration of some of the letters. For example, it may be difficult for a patient to distinguish between the letters “C” and “G.” In addition, the details of the symbols may blur as the distance from the eye increases and identification thus becomes more difficult. As a result, a clinician giving the test may credit the person taking the vision test with accurately identifying similar symbols and other times such clinicians may only give credit for identifying the exact symbol accurately. Thus, there is a subjective judgment which leads to inconsistent quantification of visual acuity. This results, in great part, because the resolution limits of the optotypes used for the visual acuity testing are not consistent. This inconsistency leads the patient to guessing what appears on the eye test chart.
There is thus a need for a visual acuity testing system and method utilizing optotypes which have a uniform resolution for all of the optotypes at the same size and distance.